The present invention relates generally to a motion stabilizer for a tractor, and particularly to a motion stabilizer in which a pendular motion of a tractor for pulling a trailer can be detected.
A trailer pulled by a tractor tends to make a side-to-side (transverse) swaying motion for some conspired reasons such as the case in which the trailer is loaded improperly. Such a swaying motion of the trailer causes the rear of the tractor to sway from side to side, making the traveling of the tractor unstable. In order to reduce the risk of undermining the traveling stability of the tractor due to the swaying motion of the trailer, JP 2002-503185 A (also published under WO99/51475A and U.S. Pat. No. 6,494,281 B1) proposes to detect a dangerous traveling condition, i.e., to determine that a pendular motion of the tractor due to the swaying motion of the trailer has occurred, if a characteristic value for a quantity describing the transverse dynamics of the tractor is greater than a threshold value, and to activate a brake upon its detection.
However, with this configuration which determines that the pendular motion of the tractor due to the swaying motion of the trailer has occurred, if the characteristic value for a quantity describing the transverse dynamics of the tractor is greater than the threshold value, the pendular motion would possibly be detected erroneously because slaloming (periodical steering-back maneuver) of the tractor which is not pulling a trailer (hereinafter referred to as “in the no-traction state”) would similarly generate great yaw rates repeatedly.
With this in view, there is a need of accurately detecting the pendular motion of the tractor due to the swaying motion of the trailer by determining whether or not a change in yaw rate observed in the tractor is derived from the swaying motion of the trailer.